Conventionally, a working vehicle such as a hydraulic shovel employs a tilt floor structure in which a floor where an operator carries out an excavation operation can be tilted up and down for securing an operation space required for maintenance and inspection, etc. around an engine.
Mounted on the tilt floor of this kind is a driving room such as an ROPS canopy employing a roll over protective structure (so called ROPS structure) and a cab where an operator can carry out operation without being drenched with rain even in the rain. The driving room such as the ROPS canopy and the cab can be exchanged and mounted on the tilt floor if necessary.
As a mechanism for assisting a tilting action relative to the tilt floor, an actuator such as a torsion bar, a hydraulic cylinder and a gas spring is used and the torsion bar and the actuator are appropriately selected or combined to be used.
Patent documents 1 and 2 propose techniques using a torsion bar as a mechanism for assisting the tilting action. Patent document 3 proposes a technique using a hydraulic cylinder.    Patent Document 1: Japanese Utility Model Publication No. 58-26864    Patent Document 2: Microfilm of Japanese Utility Model Application No. 61-14667 (Japanese Utility Model Laid-open Publication No. 62-127077)    Patent Document 3: Japanese Patent Application Laid-open Publication No. 60-143185